Early human ancestors such as Lucy, the famous Australopithecus afarensis, may have been less intelligent than modern great apes including chimpanzees, gorillas and orangutans, according to a new study.
Researchers from the University of Adelaide measured the size of canals in the skulls of living great apes and compared them to those in fossilised skulls of human ancestors. The size of these canals indicates the rate of blood flow to the brain, which is linked to metabolic rate and intelligence.
The study found that modern gorillas have twice the rate of cerebral blood flow as Australopithecus, despite having similar brain sizes. Even smaller-brained apes like chimpanzees and orangutans showed higher blood flow rates than Lucy's species.
Lucy, whose 40 per cent complete skeleton was discovered in Ethiopia in 1974 and dated to 3.2 million years ago, had a small skull and walked upright. Previous assumptions that Australopithecus had similar intelligence to great apes were based on comparable brain sizes, but the new findings suggest otherwise.
Lead researcher Roger Seymour said the results cast doubt on the idea that modern apes can serve as proxies for early human cognitive abilities. The study was published in the journal Proceedings of the Royal Society B.
